Recent studies of wildfires indicate that the flames entered the house by vents along the eaves or soffits of a house. Studies of hurricane damage on wood-frame buildings indicate that extensive damage was generated to a house by strong winds, when the roof rafters or roof trusses were torn from the outside wall. Earthquakes can shake the walls and roof at different rates, because of the weight difference, which can cause the roof and wall to separate.
Roof sheathing ties all the rafters together on a wood frame house, and the roof sheathing ties all the roof trusses together when a masonry or wood-frame house is constructed with trusses. If the rafters or trusses rack or twist from the wind forces, the roof sheathing can detach from the roof allowing wind and rain to enter the house.
Roof sheathing that is tightly secured to the rafters or trusses and subsequently fastened to the walls, helps transfer uplifting forces to the walls and henceforth to the foundation. If the roof sheathing fails, the trusses collapse, and the walls usually fall down as they can not stand by themselves against strong winds.
Roof trusses can take tremendous compression pressure, but are usually weakly attached to the top plate of the wall by toe-nailing or prior art hurricane clips. During house construction, when a rafter or roof truss is attached to the erect wall, it is usually fastened by toe-nailing or driving a nail at an angle into a thin edge of the rafter and into the top plate.
Toe-nailing is a weak, but time honored way of constructing rafters and trusses. Driving a nail at an angle usually moves the rafter off it""s correct location on the top plate. This invention forms a much stronger building connection without toe-nailing or fragile hurricane clips.
Studies of wildfires show that flames enter a house by vents along the eaves or soffits of a house. The ventilation spaces formed a chimney-effect that sucked the flames into the attic of the house. Even if the roof had fire-proof material on the outside, the flames were already inside the attic, burning from the inside. Spraying water or fire-fighting foam on the outside of the roof will not stop the flames after they have been sucked into the house through vents or other openings.
Some engineers feel that an attic does not have to be vented. The vent screens usually deteriorate over time, letting birds, bats, insects, and rodents into the attic. If a bush next to a house catches fire, even if only momentary, the flames can be sucked into the attic like a chimney. To prevent flames from entering the attic, the opening between the rafters, top plate, and roof sheathing must be tightly sealed off.
Studies of damage after Hurricane Andrew show several problems with the attachment of roof rafters and roof trusses that this invention solves.
Roof overhangs act like wings, creating huge uplifting forces during strong winds. This uplift tears apart the rafters that are toe-nailed to the header or top plate. The uplift can also twist rafters and roof trusses weakening the toenailed connections and causing detachment. Roof sheathing can be improperly attached to the rafter, and is usually covered by the roofing material. If the roof sheathing becomes detached from the underlying rafter, the house will be severely weakened, and rain will ruin everything inside.
A hurricane""s wind and pressure can push in a wall, suck out a wall, push a wall laterally, lift the rafter from the top plate, and separate the roof sheathing and roofing material from the rafter.
A Federal Emergency Management Agency (FEMA) Publication, FIA-23, xe2x80x9cBuilding Performance: Hurricane Iniki-in Hawaiixe2x80x9d shows undersized and improperly attached metal fasteners (FIGS. 26-27). Because of the shape of all roofs, wind blowing across a roof tends to lift the roof off the walls as shown in FIA-23, FIG. 48. The most important tie in an existing house is between the rafter and top plate or roof truss and top plate. Any uplifting wind force on the roof must be transferred to the walls.
Another problem with home construction is on mis-installation of prior art hurricane clips. After Hurricane Andrew, there were many examples of careless and inferior attachment of hurricane clips or they were entirely missing. One company has visited new construction sites and documented many examples of shoddy and incorrect application of their products.
During an earthquake, the floor, wall, and roof diaphragms undergo shearing and bending. The shear forces from the roof boundary members are transferred to the top of the shear wall by way of toenails to the top plate. To withstand and transfer the shear loads, the connection between the roof and wall must be strong.
Steel connectors, between different components of a wood-frame buildings superstructure, provide continuity so the house will move as a unit in response to seismic activity (Yanev, 1974).
The outside wall sheathing provides lateral stability to the walls, preventing racking. The sheathing also absorbs and transfers earthquake forces by becoming a shear wall. In order for the wall to perform as a shear wall, it must stay upright and intact. This invention makes a strong and rigid connection between the roof rafters or trusses, top plate, and wall sheathing.
Many houses are still built with the time-honored method of toe-nailing the rafter or roof truss to the top plate of the wall. This weak method drives a nail at a steep angle through a thin edge of the rafter into the top plate. Any uplifting force splits the rafter or pulls the nail out. This method was used in most places until after Hurricane Andrew devastated southern Florida.
Exact measurements are usually performed to get the rafters in the correct location, but toe-nailing or striking the rafter at a steep angle shifts the rafter even when striking it again by nailing on the opposite side. Installing this invention can cut measuring time drastically and eliminates toe-nailing so rafters or trusses are exactly on-center. Hurricane clips have been used in the past, but they are thin, weak and only tie a thin edge of the rafter and top plate together, and don""t tie adjacent rafters together.
A number of connectors have been developed to tie together the structural members of a house under construction. Up until this invention, nobody had seen how to make a connector that could tie the roof rafters together and to the wall top plate, exactly space out the distance between rafters, prevent chimney-effect of fires into the attic, tie into the roof sheathing, prevent lateral movement during an earthquake, prevent thrusting when heavy loads are placed on the roof, and prevent uplift during a hurricane.
My co-pending application, Ser. No. 09/794,998 shows a frieze board that is retrofit to the roof rafters, the top plate, and outside wall sheathing. It provides ventilation and prevents uplift, thrusting, and lateral movement. My co-pending application Ser. No. 09/516,655 and related applications show other roof plates for tying down the roof sheathing.
A leading manufacturer of wood construction connectors, the Simpson Strong-tie Company, shows no connectors in their catalog that tie the roof rafters to the wall top plate, while spacing out the distance between rafters, preventing fire from entering an attic, and tying into the roof sheathing to prevent lateral movement during an earthquake and uplift during a hurricane.
There are a number of connectors that block fires from spreading from one floor to the next, by blocking flames from rising between studs. Boscamp""s U.S. Pat. No. 6,189,277 is a firestop for metallic stud framing.
There are several connectors for rafters that provide ventilation, but they don""t prevent the chimney-effect of fire entry into the attic. Jonett, et al""s U.S. Pat. No. 5,370,577, and Luckey""s U.S. Pat. Nos. 3,777,649 and 4,126,973 vent the attic.
Hess""s U.S. Pat. No. 5,412,920 spaces beams laterally. Pearson""s U.S. Pat. No. 5,007,216 is an insulation stop at the top plate.
There are a number of ties that fasten the rafter to the top plate while a house is being constructed including: Knoth U.S. Pat. No. 5,561,949, McDonald U.S. Pat. No. 5,560,156, Colonias U.S. Pat. No. 5,380,115, Stuart U.S. Pat. No. 5,335,469, Colonias et al U.S. Pat. No. 5,109,646, Commins U.S. Pat. No. 4,714,372, Gilb U.S. Pat. No. 4,572,695, and Gilb et al U.S. Pat. No. 4,410,294.
These are good inventions, but they do not tie two rafters together or block fire from entering a house. The prior art hurricane clips provide little lateral strength, even when using a left and right. The prior art cannot tie the roof sheathing to the underlying top plate and roof rafter. They cannot prevent the roof sheathing from being blown off during strong winds of a hurricane. They do not prevent the roof sheathing from splintering and disconnecting during earth tremors.
There are several retrofit apparatus for securing roofs using cables. Adams U.S. Pat. No. 5,570,545 and Winger U.S. Pat. No. 5,319,896 are both temporary, meaning a homeowner must be home to deploy and anchor the ephemeral cables. The anchors can only be as secure as the nearby soil and the cables do not prevent the walls from bowing or blowing out.
Prior art connectors relied on angled nailing, to provide lateral support, which is complex to manufacture, and very difficult to install around structural beams. My invention effectively ties together adjacent rafters or roof trusses to the top plate to form a strong connection between the rafters, top plate, and the roof sheathing.
Accordingly, several objects and advantages of my invention are that it helps secure the roof and wall of a building to make the building a solid unit and helps prevent it from being destroyed by hurricanes, earthquakes, and wildfires.
This invention helps prevent the roof from being blown off the walls of building. It keeps the roof rafters and roof trusses tightly secured to each other and to the top plate of the wall.
This invention helps prevent the roof rafters and roof trusses from twisting during strong winds, thereby preventing detaching of the roof material and roof sheathing. It stiffens the edge of the roof and the top of the wall, helping to transfer lateral loads to the whole roof and walls.
This invention makes the top of the wall very sturdy and helps make the outside wall and roof into stable shear-walls, absorbing and transferring lateral forces into the foundation.
Many older homes were constructed with the best materials and by competent carpenters, but used the time-honored method of connecting the rafter to the top plate with nails driven into the edge of the rafter. This weak connection, called toe-nailing, is still in use today. Even if prior art hurricane clips were used in construction, the homeowner can""t tell, and those clips don""t tie adjacent rafters together to the wall, or tie the roof sheathing to the wall.
Mounted on the top plate, rafters, and roof sheathing, this invention resists uplift, one of the most destructive forces of a hurricane. Mounted on the top plate and wall sheathing, the invention helps prevents the top of the wall from bowing out by the extreme negative pressure of a hurricane.
During an earthquake, when this connector is mounted on the roof and walls, they will help make the walls and roof stiffer and therefore into shear-walls. The secured wall-roof junction will absorb and dissipate earth movements, without becoming detached from each other.
This would improve the house beyond existing building codes, as sheet metal joints have been proven to perform better than nailed joints during hurricanes and earthquakes. Existing building codes have no knowledge of how to tie the roof sheathing to the top plate.
Another object of this invention is to prevent the entry of fire into the attic from wildfires. Studies of recent wildfires have shown that houses having fireproof roofs still had their roofs on fire, even though there was no visible entrance for flames. Vents on the eves or soffits formed a chimney-effect, drawing in the flames. This invention seals the area between the roof and wall to prevent the entry of fire, while preventing uplift and lateral movement.
Yet another advantage of this invention is during earthquakes, nails can sometimes bend with the movements of the house, but screws often break. Even though screws hold tighter than nails and provide a tight connection against uplifting forces from hurricanes, they are less resistant against earth movements. This invention absorbs and transmits most of the forces during an earthquake and hurricane so nails and/or screws can be used as fasteners.
Another advantage is that since the invention absorbs and transfers earthquake and hurricane forces, less nails and nailing could be used. Also, screws could be used in the invention in earthquake areas with less fear that the heads will shear off.
Still another advantage is that with the roof rafters and roof trusses better able to resist twisting, roof sheathing will stay firmly attached and roofing material will now have a better chance of staying on during strong winds and earth movements. In addition, with the sheathing now firmly connected, new materials may be attached to the roof, such as solar electric panels, without fear of them being blown or shaken off.
In areas with brush or forest fire danger, fire-proof material or heavy material, such as long-lasting tile, stone or metal, can now be applied to the roof with less danger of being blown or shaken off during earth tremors or high winds. The invention resists thrusting, or the weight of the roof pushing outward on the wall, since the heavy weight of the roof is now securely attached to the wall.
Earth tremors and hurricanes always destroy the weakest parts of a house. By making the vertical walls and roof envelope into a strong unit, there will be less damage.
It is a further object of this invention that it easily, quickly, and economically protects houses from the destructive forces of earthquakes, hurricanes, and wildfires. It is a still further object that the connectors and fasteners are strong, attractive, permanent, functional, uncomplicated, simple to manufacture, easy to install, and economical. The embodiments can be made from a single sheet metal blank, without any welding.
Many houses are still built with the time-honored method of toe-nailing the rafter or roof truss to the top plate of the wall. This weak method drives a nail at a steep angle through a thin edge of the rafter into the top plate. Any uplifting force splits the rafter or pulls the nail out.
Exact measurements are usually performed to get the rafters in the correct location, but toe-nailing or striking the rafter at a steep angle shifts the rafter even when striking it from nailing on the opposite side. Installing this invention between rafters or trusses cuts measuring time drastically and eliminates toe-nailing so the rafters or trusses are exactly on-center.
A further object is that this invention can be used on various size sheathing, rafters, roof trusses, studs, wood or metal I-beams, TJI, and glue-lams, all made from wood or metal. There may be insurance discounts for homeowners who have this invention installed on their houses.
Traditional toe-nailing of the rafter is at the bird""s-mouth, a notch cut into the rafter where it rests on the top plate. By cutting out material from the rafter, a bird""s-mouth weakens the rafter. Toe-nailing only two nails from either side grasps only a small edge of the rafter, and the nail only extends into the top 2xc3x97 of the top plate. This invention can make cutting deep birds-mouths into the rafter unnecessary.
This invention is adjustable, using a double-bend, in order to fit the variable heel height at the rafter, caused by different roof slopes.
Tests were done by the Colorado School of Mines on my co-pending hurricane clip, application Ser. No. 09/191,852. The tests showed that the rafter split lengthwise, due to uplifting force, before the clip failed. Rafter tabs and gussets on this invention may prevent the rafter from splitting, and will hold it together even if the rafter splits lengthwise at the connector.
This invention strengthens the rafter to top plate connection by vastly increasing the spacing and amount of nails in the thickest part or xe2x80x9cmeatxe2x80x9d of the rafter. This clip also strengthens the bird""s mouth by wrapping on either side of the rafter and keeping it from splitting along the long measure. By placing members and fasteners on both sides of the front face and into the rafter, strength is increased tremendously.
Another advantage is with two adjacent rafters tied together and to the top plate, it tremendously increases resistance to thrusts. This makes the roof much stronger and able to resist more weight such as thick snow, ice, or volcanic ash, and heavy roofing material such as tile, insulated roofing, solar collectors, and satellite dishes.
This invention takes the place of a left and right prior art hurricane clip, thus cost and installation time is substantially reduced. Installation can be accomplished with a hammer, power nailer, or powered screw gun.
Since this invention fills the space between rafters, wood blocking does not have to be cut to fill the space, thus saving trees and labor. The invention can be made from recycled steel. By forming a box-like section, torsional twisting is significantly reduced over prior art hurricane clips. Cross-grain splitting, where the sheathing pulls away from nails driven on its edge, is avoided with this invention and its large surface area on the wall sheathing, and on the roof sheathing.
The left and right rafter tabs, that are installed on opposite sides of the rafter have offset nail holes. Nails driven into the rafter will be offset from each other lessening wood splitting and vastly increasing holding power. Fasteners into the top plate are on adjacent sides of the top plate. This holds the top plate together and puts nails in shear. To move up, down, in, out, or side to side, some nails must be sheared.
By drilling a hole in the roof, and adding a simple roof plate, bolt, and nuts, the roofing material and roof sheathing can be held down to the roof rafter. This invention can hold down the roofing material and roof sheathing to the rafter or roof truss, providing great rigidity to the entire house. This makes the house significantly more resistant to uplift from strong winds, and lateral movements from earth tremors.
These and other objectives of the invention are achieved by simple and economical connectors that allow a builder to quickly and easily secure the weakest parts of a building against wildfires, earth tremors, and high winds.
Advantages of each will be discussed in the description. Further objects and advantages of my invention will become apparent from a consideration of the drawings and ensuing description.